Biosynthesis of Polyhydroxyalkanoates (PHAs) by the Valorization of Biomass and Synthetic Waste

Abstract

Synthetic pollutants are a looming threat to the entire ecosystem, including wildlife, the environment, and human health. Polyhydroxyalkanoates (PHAs) are natural biodegradable microbial polymers with a promising potential to replace synthetic plastics. This research is focused on devising a sustainable approach to produce PHAs by a new microbial strain using untreated synthetic plastics and lignocellulosic biomass. For experiments, 47 soil samples and 18 effluent samples were collected from various areas of Punjab, Pakistan. The samples were primarily screened for PHA detection on agar medium containing Nile blue A stain. The PHA positive bacterial isolates showed prominent orange–yellow fluorescence on irradiation with UV light. They were further screened for PHA estimation by submerged fermentation in the culture broth. Bacterial isolate 16a produced maximum PHA and was identified by 16S rRNA sequencing. It was identified as Stenotrophomonas maltophilia HA-16 (MN240936), reported first time for PHA production. Basic fermentation parameters, such as incubation time, temperature, and pH were optimized for PHA production. Wood chips, cardboard cutouts, plastic bottle cutouts, shredded polystyrene cups, and plastic bags were optimized as alternative sustainable carbon sources for the production of PHAs. A vital finding of this study was the yield obtained by using plastic bags, i.e., 68.24 ± 0.27%. The effective use of plastic and lignocellulosic waste in the cultivation medium for the microbial production of PHA by a novel bacterial strain is discussed in the current study.

Production of polyhydroxyalkanoates (PHAs) by Bacillus megaterium using food waste acidogenic fermentation-derived volatile fatty acids

“…The results obtained are in accordance with previous studies stating the faster assimilation of carbon sources such as glucose and acetic acid compared to that of longer and branched volatile fatty acids [40]. Furthermore, it should be noted that the rate of carbon assimilation can highly depend on the environmental factors of temperature, pH and oxygen demand which directly affect bacterial activity [45][46][47]. For example, in this case Bacillus megaterium is a mesophilic bacterium, which grows in an optimal temperature of 30-37°C [48].…”

Study of The Fermentation Conditions of the Bacillus Cereus Strain ARY73 to Produce Polyhydroxyalkanoate from Glucose

“…No PHA production occurred at 40 °C, while the strain was able to grow with a Cell Dry Weight of 3.41 and 2.51 g/L at 48 and 96 h, respectively, this indicates that the higher the Cell Dry Weight does not necessarily imply an increase in PHA production. Javaid et al [2020] demonstrated that the Stenotrophomonas maltophilia strain IAM 12423 showed poor decline in PHA yield at a temperature above 37 °C, while still recorded high amount of CDW.…”

Short Communication: Isolation and screening of polyhydroxylalkanoates producing microorganisms from Thailand

“…Polyhydroxybutyrate (PHB) is produced from community wastewater with Enterobacter aerogens 12Bi strain (Ceyhan and Ozdemir 2011). Javaid et al (2020) reported PHA production from waste, such as wood chips, cardboard cutouts, plastic bottle cutouts, shredded polystyrene cups and plastic bags, using Stenotrophomonas maltophilia HA-16 with good yield. The bacterial isolates B2 (Enterobacter carcerogenus) could be considered as potential strain for the conversion of rice straw hydrolysate into PHA.…”